This information is put here because if you’re just starting the game, the infector is one of the most unappreciated guns in the game, and you may not know exactly how its mechanics work!

I’ve used Infectors and BMGs almost exclusively since I first found a version of either.

The main thing to keep in mind when using Infectors, is that the damage over time isn’t equivalent to the “infected” indicators, the DoT runs out quite a bit before the indicators dissapear – so you’ll need to refresh it more often than you think.
That being said, what kept me using them in almost every situation, is due to a couple of reasons:
– Infecting multiple enemies means you can spread the damage across multiple enemies faster. Granted, not as fast as a BMG under perfect conditions. Nor do they do as high single target damage as other weapons, but that’s where the second reason comes in:
– Spreading out your DoT’s will eventually start to result in compounded damage, a chain-reaction so to speak.
Once the first enemy dies, the bugs hatched will severely damage the next target – either by just a single one of the spawned bugs, or all of them. If you’ve “done your job” and kept the infected rating going on that enemy as well, the resulting bugs from that enemys death, who should be low on health by now as well, will further increase the wave of damage. Ultimately, the more you’ve been able to spread out your infections, the more damaging a wave of bugs you can create – kind of like “throwing pebbles into a pond will manifest a tsunami”.
The downside is, of course, that while you’re throwing pebbles, you could be hurling rocks – but I find the resulting damage is well worth the wait, simply because, as meantioned above, you can keep the damage going on multiple enemies, and as a result, multiply the result once you start to actually kill the enemies.

As for the variations:
Personally, I prefer the “Canker” and “Invader” variations because of the high rate of infection.
– In the Cankers case, the increased DoT makes up for the lack of bug damage, and yet the resulting bugs hatched when the target dies still allow you to build up the previously mentioned wave.
– As for the Invader, it relies more heavily on bugs, and will spawn a bug for each infection indicator. It’s basically a more “fire and forget” version of the Canker, and you can spread out your damage more without having to focus on several enemies – the trade-off being that it will take a bit more time to get the ball rolling.

I’ve mainly focused on those two variation, but my experience with the other variations are:

– The Inflictor is more or less the same as the standard “Infector” variation. I believe it is bugged (no pun intended), and that it should actually spawn one extra bug per infection indicator (every 5 shots), or 2 bugs per 5 shots. But since it doesn’t, it has the exact same stats and behaviour as the normal variation.
– The Inoculator is the crowd-control version. Instead of spawning bugs, it spawns “globs” that slow down the enemy. Basically, it makes it easier to spread the infection, but at the price of no additional bugs nor increase in damage over time.
– The Immunizer is, well, what it says it is; the long distance version. Usually the increased distance isn’t all that useful, but can be a convenience at times. Obstacles or sheer number of enemies, along with the inability to fire accurately due to the lack of “manual” aim, results in the effectiveness falling somewhat short in the situations it was designed for.
– The Outbreaker, if I recall correctly, is more or less the “extreme” version of what the Inflictor should supposedly be. It gives you bugs faster, for the price of slightly more shots (3 shots per bug), but doesn’t do much, if anything, in the way of DoT outside of that – again, if memory serves. The major difference between the Outbreaker and the “intended” Inflictor, is that your army’o’bugs should hatch slightly faster, and be slightly easier to maintain.

If I’ve gotten some of the names and actual mechanics mixed up, I apologize, in some cases I’ve nearly never used a given variation, so the connection between name and mechanic are a bit fuzzy.

So the way I try to use my Infectors, is by infecting as many targets as possible first, and once that’s done, keep the DoT going on a single target. If that target takes a while to kill, I refresh the infections on the other targets, but don’t worry too much about the “Infected” DoT on them, only that they will have at least some active infections going on them by the time the rush of bugs from my primary target reaches them.

On a final note, each consecutive 5 shots will trigger a comparatively large burst of damage. I’m unsure as to whether or not it adds another DoT, or if that’s capped at 3x.
In any case, any perk that increases your reload speed helps you spread the infections faster, and since that’s almost literally “the name of the game” with these weapons, decreasing the time it takes to either infest or hatch bugs, either by reload speed or magazine size, is what I find to be the most useful bonus for these weapons.

Update:

Oddities about the stat information worth noting:
– DoT is not indicated by the Infection indicators. It stops a good while before the infection “clears”.
– All parasites deal ~500 damage when they detonate on an enemy, regardless of variation.
– Individual shots will hit for the damage stated, but every time an infection is applied, a damage burst of ~600 will trigger, and in most cases a parasite will spawn.
– “Bug DMG” actually refers to the DoT applied per infection indicator, up to a maximum of 3x the number shown (3 infections applied)
– All variations will spawn bugs upon enemy death.

Afflictor: “Spawns parasites whenever a target has been hit five times”
This is more or less the same as the standard “Infector” variation. I believe it is bugged (no pun intended), and that it should actually spawn one extra bug per infection indicator (every 5 shots), or 2 bugs per 5 shots. But since it doesn’t, it has the exact same stats and behaviour as the normal variation.

Canker: “Does not spawn parasites but infections deal increasing damage over time”
– Does not spawn parasites upon infection.
This has the highest DoT among the variations, but it does not spawn any bugs except upon enemy death.
It shares the shortest range and slowest refire rate of all the variations, along with the Invader. (The difference in refire-rate is countered by it not being burst-fire)

Immunizer:
Has extended range, but other than that, behaves as the standard variation.

Incubator: “Applies a slowing effect to infected targets restricting their movement”
– Does not apply DoT upon infection.
– Spawns 2 parasites per infection.
This relies solely on parasites for damage, and does not apply any DoT. Aside from that, it behaves in much the same way as the base variation.

Infector: “Causes parasitic infection of the target which then burst allowing the release of alien life forms”
The Vanilla version. It applies DoT and spawns parasites upon infection, but has no advantage except having no particular disadvantages.

Invader: “Fully automatic version of the infector allows for quick infection of targets”
This is both fully automatic – as stated – and spawns bugs upon infection. It’s DoT is, however, the same as the base variation.

Outbreaker: “Spawns parasites whenever a target has been slain while infected”
– Does not spawn upon infection.
This variation is somewhat like the Canker, in the sense that it does not spawn any parasites when applying one infection mark (every 5 hits). It does, however, have slightly different stats compared to the Canker: It does less damage over time – but more than the other variations, and has a longer range.

So, to sum it all up:
Canker has the highest DoT, but doesn’t spawn parasites on infection, and has the shortest range.
Invader has the second highest spawn-rate of parasites, as well as DoT, but shortest range.
Incubator slows enemies, the highest spawn rate of parasites (2 on infection), but has no DoT.
Afflictor is possibly bugged; it spawns 1 parasite on infection like most other variations.
Outbreaker second highest DoT with increased range, but doesn’t spawn parasites on infection.
Immunizer has the farthes reach, but nothing else.

Personally, I prefer the Canker for PvP – as the parasites that usually spawn can take a while to “activate” and find a target, by which time you’ve most likely been deadified if they were spawned because of applying an infetion, as opposed to the opponent being killed.
As for PvE, I normally go with Invader because of the high overall damage (average DoT, second highest spawn-rate of parasites – which makes it good for dealing with crowds of nasties).

But, it is as with everything else, a matter of preference.
Both the Canker and Invader have the shortest range, so they require you to get closer to the nasties.
Conversely, Immunizer and Incubator would be good for crowd-control, PvP and PvE alike.
And finally Infector – and Afflictor because of the possible bug listed above – are the happy middleground of all.